Modeling of Battery Systems and

Installations for Automotive ApplicationsRichard Johns, Automotive Director, CD-adapco

Robert Spotnitz, President, Battery Design

Predicted Growth in HEV/EV Vehicles

Source: Hiedge

3

Typical HEV Battery Installation

Picture A123

4

HEV Battery Installation

Picture Daimler

5

EV Battery Installation

Cooling Outlets

6

EV Battery Installation

Cooling Outlets

7

• Li-ion batteries offer the most likely route to HEVs and EVs and

are being actively pursued by most OEMs

• However, there are many issues to be resolved:

Cost, Lifetime, Durability, Safety

Rapidly developing battery technology

• Many of the important technical problems incl. Lifetime,

Durability, Safety, are related to high temperatures and thermal

management is one of the critical issues to be resolved

• CD-adapco and Battery Design LLC are investing heavily to have

the right software tools available for the analysis of battery pack

and vehicle installations

Issues to be Addressed

Thermal Management: Cooling Strategies

Air cooling

Refrigerant

8

E-compressor

Air Evaporator

Chiller

) (

Coolant circuit

Battery

Pump3 41

TXV

2

5

6

co

nd

en

se

rra

dia

tor

Battery

Liquid cooling

9

Battery cooling of various cells types

Source: Behr

10

Typical cell internal construction details

Source: Behr

• Load cases:

Drive-Cycle

Hot soak

High-rate charging

Cold start

Thermal Management

t(s)

Pelec

(W)

• Assessment Criteria:

T uniformity (Δ < 3 °C)

Top ~ 35 °C, Tmax < 55 °C

Cooling system parasitic losses

Safety – thermal runaway

Source: NREL

12

CD-adapco and Battery Design LLC

Partnership

CD-adapco and Bob Spotnitz, one of the world’s foremost battery

system modelers and President of Battery Design LLC, have formed a

partnership to develop a full flow-thermal-electrochemistry capability

in STAR at the cell, pack and installation levels

CellInstallation Pack

Picture Behr

13

CD-adapco and Battery Design LLC

Partnership

Battery Design LLC: Detailed modeling of the cell electro-chemistry

CD-adapco: Detailed 3D modeling of the flow, thermal and stress

The Partnership will deliver a transient, fully-coupled

simultaneous solution of the flow-thermal-electrochemistry

STAR-CCM+: Total Vehicle Thermal Protection

Extensive validation has been carried out in many areas

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It is NOT possible to predict cell performance solely from design data

Cell Models

• There are 2 levels of complexity for modeling cell behaviour:

1) Simple Circuit Model: Experimental data is used to determine the

coefficients of a curve fit over a range of battery operating

condition. This model is recommended for thermal studies within

the range of fitting.

2) ElectroChemistry Model: A detailed model of the cell physics.

Requires both experimental data AND detailed knowledge of the

cell design. This model would be necessary to predict behaviour

beyond the range of the experimental data (eg thermal runaway) or

for extended physics models (eg Li plating)

Identical cell models are implemented in STAR-CCM+ and Battery

Design Studio ® used to set up the parameters of the model

Battery Design LLCSoftware for Battery Design and Simulation

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Development started April 1999

Battery Design Studio®

the means to model batteries

•To analyze data

•To visualize cell designs

•To compare experiments with

models

•To visualize model results

•Database

InputModels

Output

Size

Cost

Power

Impedance

Life

Abuse, etc

Data

Lab

User

17Page 17

Five parameters

OCV, OCV’, Ro, Rp, C

Simple Circuit Model

Example shows level of fit with experimental data for a discharge/charge cycle

18

Unit Cell Electrochemistry Model

• Coupled to sizing programs in Battery Design Studio ® –

all geometry information set up automatically

• Temperature and concentration dependent solid-phase

diffusion coefficients – important for accuracy over a

wide range of conditions

• Multiple active materials – common feature of many

contemporary design of batteries

• Side reactions (lithium deposition – component of

ageing, self discharge)

• Choice of kinetics expressions (linear, Tafel, Butler

Volmer)

Enhancements to the standard model

Cycle 1

Cycle 9

Electrochemistry model

Example shows level of fit with experimental data for a discharge/charge cycleExample shows comparison between measurements and simulation for a

HPPC (High Pulse Power Characterization) Test

21

Electrochemistry model

Example shows level of fit with experimental data for a discharge/charge cycleExample shows comparison between measurements and simulation for a

C/5 discharge > charge > C/2 discharge > charge > C discharge > charge > 2C

discharge cycle

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Coupled Flow-Thermal-Electrochemistry solution process

• All cell models – simple circuit to full electrochemistry are available in

STAR-CCM+

• The electrochemistry models used in STAR-CCM+ and Battery Design

Studio ® are identical

• BDS is used to set up the cell characterization, given the cell

measurement and design data. The output is the TBM file

• Simple circuit cell models are relatively straightforward to set up and

users can be easily trained to do this

• Full electrochemistry models are more complicated to set up and

require assistance from Battery Design LLC

• The STAR-CCM+ solution is fully coupled at time-step level between

the flow, thermal and electrochemistry models

Electrical Model

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Battery and cell electrical connections and current flows are included in the

model. Cell mapping (far right) shows discretisation of a prismatic cell to

allow for spatial variations within a cell

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The Engineering Process

Solver &

Postprocessing

Cell

Characterization

Li-ion cell

knowledge

Build CFD Model

CFD

Knowledge

Li-ion cell

& CFD

knowledge

Cell design

Cell measurements

Battery design

BDS

STAR-CCM+

STAR-CCM+

Boundary Conditions

TBM File

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Summary

All major auto OEMs have programs for electric vehicles for a rapidly

growing worldwide market

Battery technology is a key enabler and differentiator BUT thermal

issues strongly influence lifetime, durability and safety

CD-adapco and Battery Design LLC have formed a partnership to

jointly develop a coupled flow-thermal-electrochemistry solution for

cell, pack and installation level simulation

This new capability will be available in STAR-CCM+ June 2010